The Earthquake Reminded Us of the Need to Increase Social Communication

Turkchem 25 Dec 2019 95 7 dk okuma

TURKCHEM

An earthquake with a magnitude of 5.7 and a depth of 11.9 km occurred off Silivri in Istanbul (Sea of Marmara) on 26 September 2019 at 13:59:24. The most severe earthquake since the 1999 Marmara Earthquake, it directed our attention back to reviewing the structures we inhabit. Why the Marmara Earthquake, why is Istanbul so important? Due to my work, I visit many cities throughout the country. During these visits, there are complaints mixed with frustration: "Everything is done for Istanbul, what's so special about it?" Despite my family originating from Elazığ, we have lived in Istanbul for approximately 80 years; we are Istanbullites. According to the Revenue Administration Directorate's 2017 Annual Activity Report, a total tax debt of TRY 760.214 billion was accrued nationwide last year, including amounts carried over from previous years. Of this amount, TRY 625.512 billion was collected. For Istanbul: accrual: TRY 326.234 billion, collection: TRY 275.34 billion, collection rate: 84.40%, Istanbul's share of total accrual: 44.4%. Istanbul is therefore extremely important. However, relative to the taxes it generates, Istanbul receives a smaller proportion from Turkey's budget. In this case, it could even be said that investments made in Istanbul are insufficient. Istanbul's growth to this extent is not technically sound. If an expected magnitude 7 or higher Marmara earthquake occurs, loss of life and property will be substantial. There is a serious risk for our country. A shift to horizontal urban development is urgently needed, and expansion should be provided starting from neighbouring provinces. Steel reinforcement and concrete determine the skeleton of a reinforced concrete structure. The producers of steel are known and inspection is possible before it enters the mould. However, ready-mix concrete is different. Because it is not ready. It is prepared on demand at that moment and shipped. Therefore, concrete must be kept under close control from its fresh state until it hardens. There are sufficient laws, standards, and regulations regarding concrete design. Ready-mix concrete facilities are highly developed and machinery production has minimised error margins. Despite this, concrete—composed of cement, water, aggregate (sand, stone dust, coarse aggregate 1 (5-12), coarse aggregate 2 (12-20)), chemical additives, mineral additives, totalling eight components—unfortunately cannot be adequately inspected. Because the human factor enters at every stage. The person who produces ready-mix concrete is different from the person who places it in the mould. In developed countries abroad and with some local ready-mix concrete producers in our country, the ready-mix concrete company that produces the concrete should also place it in the mould and carry out curing. Therefore, the intervening human factors will be eliminated. Subcontractors should form an organisation under the ready-mix concrete company. This practice is expected to become more widespread in the future. Revisions have been made to the building inspection regulations. Accordingly, inspection of concrete laboratories with chipped concrete samples has become necessary and mandatory. An extremely appropriate decision. However, even if the design of fresh concrete is perfect, proper placement and maintenance processes must be carried out within required standards. The understanding that profit remains with the builder, the exploitation of this situation by economically and politically influential people, and ill intent create problems in implementation despite perfect standards, legislation, and regulations. This also negatively affects basic income distribution. Only ethics, social self-regulation, and the rule of law solve the problem. 2019 was declared 'pedestrian priority traffic year.' According to regulations, vehicles must yield to pedestrians. Social responsibility and awareness must become widespread. For example, when the front vehicle driver allows a citizen to cross at a pedestrian crossing, the rear vehicle driver must also take their own precautions. They should adjust braking distance accordingly, not sound the horn, and not engage in bad behaviour. The pedestrian should only cross at locations with pedestrian crossings, not cross from the middle of the road or jump from the median as they please. Ensuring conscious social self-regulation will enable us to become more civilised in sanitation, health, education, and human relations. After these anecdotes, let us examine "What Can We Do" for our structures against earthquakes.

A-) Concrete Cover

Most structures in our country are reinforced concrete. The durability of reinforced concrete depends on the steel reinforcement it contains. That is, if the steel reinforcement inside a reinforced concrete building is damaged by corrosion and loses its continuity, the structure collapses. The better the concrete wraps around the steel, the longer the building's lifespan. To save on usable floor area (m²) within the structure, unfortunately even concrete cover has been reduced in calculations. Consequently, some reinforcement has become exposed to corrosion. Also, to save space, plaster was not applied to these surfaces. Plaster was applied directly over them. As a result of direct plaster contact with concrete, corrosion has begun in new buildings as well. While a rough concrete primer is sometimes applied to reinforced concrete before plaster, uniform application is not carried out everywhere. In fact, rough concrete primer is not even used on many surfaces outside the ceiling slab. While costs are a consideration, the value of a lost life cannot be measured. For this reason, the formwork system should be reviewed. Deformed formwork resulting from excessive use should not be used. Attention should be paid to the type of mould release oil. In short, concrete cover must definitely be provided and its variety should be increased. Abroad there are many examples of concrete cover. Using only plastic spacers may be insufficient.

B-) Semi-Detached Structures

In some semi-detached buildings, no gaps have been left between structures. During earthquake oscillations, both reinforced concrete frames collide with considerable force. The result of the collision creates structural cracks. Another damage is waterproofing problems. Initially, there is no gap or only 1-2 cm, but after earthquakes, separations of 5-15 cm are observed. Water entering from both the building facade and the roof terrace negatively affects living comfort. Water ingress causes plaster to flake, paint to blister, and corrosion to form in the structure. Research has shown an increase in diseases such as COPD, asthma, and bronchitis. As if there were a dilation gap in the structure, such areas must definitely be repaired with bitumen-polyurethane-based products. The interior of these gaps should not be filled with rigid, cement-based products. Because rigid material will crack as a result of movements during earthquakes.

*Note: The levelling screed application shown in item 9 of the chart applies to horizontal surfaces. For vertical surfaces, it should be considered to close with thermal jackets etc.

C-) Basements must be addressed again. Closed parking basements and basement levels should not exceed a basement height/building height ratio of 1/6. That is, if basement height is 3 m, building height should not exceed 18 m. If proper reinforcement and concrete quality have been correctly selected during the design phase, this rule can be modified. Basement levels are overlooked because they are not visible to unit owners. A pergola to be built in the garden, the colour of the external facade paint, or a tree to be planted sometimes cause greater disputes. "Even if we bury our heads in the ground like ostriches, the structure is visible." Reinforced concrete surfaces should not leave steel reinforcement exposed. In some places, instead of plastering, lime or plaster is applied. This is extremely dangerous. Even without environmental corrosion, it initiates corrosion and accelerates it. If there is a crack in the reinforced concrete, whether it is progressing should be monitored. If covered, detection becomes impossible. Proper waterproofing should be carried out from the direction water arrives, that is, from the positive side. In semi-detached basement levels, waterproofing should be done by excavating around the building. However, this application is not carried out due to the thought that it will be costly. Basement levels are structurally important. If possible, waterproofing should be done from outside, otherwise from inside. Interior waterproofing is not entirely correct. Because even if you prevent water from entering the structure, you cannot stop corrosion forming in the steel. As shown in the photograph, a small drainage channel has been created so water does not spread and can be directed. However, these methods will not prevent the steel inside the reinforced concrete from eroding due to corrosion. The tray method shown in the photograph on the right above is also unfortunately a frequently used system. Here you can collect water in a certain place and drain it from there, but you cannot prevent corrosion in the steel.

D-) Hollow Block Flooring

No public buildings (generally) are constructed using foam hollow blocks. The private sector builds multi-storey structures from foam hollow blocks so work proceeds quickly and serially. The foam blocks used also lack density and are products highly sensitive to temperature. Some problems arising in structures constructed using foam hollow blocks are as follows: 1) It is not suitable for use in earthquake zones because the frame cannot be fully formed. 2) It should not be used without reinforced concrete shear walls. 3) Due to these low-rigidity beams, horizontal inter-storey displacement during earthquakes becomes very large and transmits very large secondary moment effects to the columns. 4) Hot air expands and rises. The foam produces harmful gases due to the surface contacted by heated air. 5) During fire, these foams will immediately ignite and spread. 6) As a result of earthquakes and other oscillations, ceiling plaster falls. Sometimes the foam itself is dislodged and falls below. If there are children, injuries and material damage occur.

Hollow Block Flooring Examples

Since 2018, the earthquake regulation (Turkey Building Earthquake Code – TBDY) has changed. Prof. Dr. Mehmet Nuray Aydınoğlu from Boğaziçi University Kandilli Observatory and Earthquake Research Institute has commented on the limitations imposed on building load-bearing systems with hollow block flooring, which should be researched and read from sources. Prof. Aydınoğlu, in summary, concluded that: in hollow block floored buildings with DTS (Earthquake Design Class) = 1,2 and BYS (Building Height Class) ≥ 6, shear walls in both directions must satisfy the overturning moment condition given in Eq. (4.3) in 4.3.4.6. Otherwise, hollow block flooring systems (for BYS definition, see Table 3.3): • (a) Cannot be used in buildings with DTS = 1,2 and BYS ≥ 6 (Hn,max = 17.5 m), • (b) Can be used in buildings with DTS = 3,4 and BYS ≥ 7 (Hn,max = 17.5 m).

In Summary

The topics above can be multiplied by providing many more examples. According to conducted research, a building without waterproofing loses 66% of its load-bearing capacity after 10 years. That is, a column measuring 80x60 cm carries 100 tons of load, whereas without waterproofing it carries only 34 tons. Therefore, in apartment buildings and residential complexes, solutions should be sought within social understanding and empathy. When an earthquake comes, the situation of someone living on the first floor is the same as someone on the eighth floor. The damage condition of the building and its oscillations during the earthquake may differ by floor. However, the psychology and fear during an earthquake are the same. Unit residents living on the ground floor or top floor of the building must address the building's problems. Waterproofing, corrosion, and cracks and damage in reinforced concrete are common issues for all unit owners.